Which organ processes drugs and changes their chemical structure?

The liver is the primary organ responsible for processing drugs and altering their chemical structure, a process known as drug metabolism. When a drug enters the bloodstream, it is transported to the liver, where enzymes work to chemically modify the substance. This modification can enhance the drug's effectiveness, aid in its excretion, or reduce its toxicity, depending on the specific drug and the metabolic pathways involved.

The liver’s extensive blood supply and highly specialized cells enable it to efficiently metabolize various substances, including medications. Factors such as age, genetics, and existing liver conditions can influence the liver’s ability to process drugs, making this organ crucial in pharmacology and therapeutics.

The other options, while important organs in their own right, do not primarily function in drug metabolism. The stomach is responsible for the initial digestion of food and absorption of nutrients, the kidneys are primarily involved in filtering blood and excreting waste products, and the spleen is involved in immune function and blood filtration. Thus, the liver clearly stands out as the essential organ for drug processing and chemical alteration.